In oil production, primary operations are frequently ineffective in recovering a substantial proportion of oil-in-place, often leaving as much as 60-80% of the oil as residual. It is common, therefore, to employ so called secondary or tertiary methods to obtain additional oil. One such secondary or tertiary method involves flooding the producing formation with an oil displacement fluid, such as water, steam, gases, etc. through one or more injection wells spaced from the producing wells. As the leading edge, or front, of the flood fluid progresses through the formation, oil in the formation is pushed towards the producing well. Where plural injection wells are used, fluids from neighboring wells may emerge to form a combined front, and such combined front may indeed completely surround a producing well.
In general, the geological and fluid properties (saturations, permeabilities, etc.) of hydrocarbonaceous zones cause uneven forward movement of native or injected fluids. In addition, the extent of an even fluid movement increases with hydrocarbon recovery, field operations and type of well pattern used in enhanced recovery operations.
Often a format ion or reservoir may contain zones of varying degrees of permeability. During a water flood or other recovery method, hydrocarbonaceous fluids may be removed from a higher permeability zone while a lower permeability zone retains hydrocarbonaceous fluids. These retained fluids often cannot be removed without blocking off the zone of higher permeability and diverting the injected fluid to the zone of lower permeability.
Also, wells are frequently completed where there are zones of varying permeabilities. In most cases, the higher permeability zones have a greater tendency to accept acids and fracturing fluid thus minimizing the effectiveness of treatment and stimulation of lower permeability intervals. Sometimes, the higher permeability zones can be isolated mechanically. However, wellbore equipment (tubing set through a permanent packer, e.g.) may limit the ability to mechanically isolate a zone. If the high permeability zone is in the lower part of the wellbore, rock salt, sand, high density plugs, or a combination of these materials can be used to isolate the interval. However, if the high permeability zone is in the upper part of the wellbore, diversion becomes considerably more difficult.
Therefore, what is needed is a method to temporarily isolate an upper high permeability zone while treating a lower permeability zone to increase its permeability for the increased production of hydrocarbonaceous fluids.